Missing References

About this errors? ok some are obvious but any dependency check list would be great, look:

Warning 1 The referenced component 'Ingres.Client' could not be found.
Warning 3 The referenced component 'MySql.Data' could not be found.
Warning 4 The referenced component 'Oracle.DataAccess' could not be found.
Warning 6 The referenced component 'System.Data.SQLite' could not be found.
Warning 7 The referenced component 'Ingres.Client' could not be found.
Warning 8 The referenced component 'nunit.framework' could not be found.
Warning 9 The referenced component 'nunit.core' could not be found.
Warning 15 The referenced component 'MySql.Data' could not be found.
Warning 20 The referenced component 'Npgsql' could not be found.
Warning 25 The referenced component 'FirebirdSql.Data.FirebirdClient' could not be found.